An evaluation of the influence of stock origin and out-migration history on the disease susceptibility and survival of juvenile Chinook salmon

Various methods have been developed to mitigate the adverse effects of the Federal Columbia River Power System on juvenile Pacific salmon out-migrating through the Columbia River basin. In this study, we found that hatchery-reared spring Chinook salmon Oncorhynchus tshawytscha in the river are in varying degrees of health, which may affect delayed mortality and the assessment of the effectiveness of management actions to recover listed stocks (e.g., barging fish downstream versus leaving fish in the river). A laboratory disease challenge with Listonella anguillarum was completed on fish from Rapid River Hatchery and Dworshak National Fish Hatchery (NFH) with different out-migration histories: (1) transported by barge, (2) removed from the river before barging, or (3) left to travel in-river. Barged fish from Rapid River Hatchery experienced less mortality than fish from Dworshak NFH. No statistical differences were found between the hatcheries with fish that had in-river out-migration histories. We suggest that the stressors and low survival associated with out-migration through the hydropower system eliminated any differences that could have been present. However, 18-25% of the fish that were barged or collected before barging died in the laboratory before the disease challenge, compared with less than 2% of those that traveled in-river. Owing to disproportionate prechallenge mortality, the disease-challenged populations may have been biased; thus, they were also considered together with the prechallenge mortalities. The synthesis of prechallenge and disease-challenged mortalities and health characteristics evaluated during out-migration indicated that the benefit of barging was not consistent between the hatcheries. This finding agrees with adult survival and delayed mortality estimates for the individual hatcheries determined from adult returns. The results suggest that the health status of fish and their history before entering the hydropower system (hatchery of origin and out-migration path) are critical variables affecting the conclusions drawn from studies that evaluate mitigation strategies.     

The use of the log-linear model to evaluate the effects of three herd factors on Streptococcus agalactiae mastitis occurrence in California, 1977

Epidemiologic relationships among Streptococcus agalactiae infected dairy herds and herd size, location and California Dairy Herd Improvement Association (CDHIA) participation were examined using log-linear methodology. Dairies located in five out of the six California Bureau of Animal Health veterinary districts were studied. Data sources included the Dairy Cattle Data Base, which uniquely identifies each of the 2875 dairies in California, the 1977 statewide CDHIA year-end summary report and microbiological results from a 1977 statewide survey of bulk tank milk samples. These data were merged, fitted and the best model selected using likelihood-ratio statistics. The model included all four “main effects”, the six possible “1st-order effetss” and the “2nd-order effect” due to the interaction of herd size, location and CDHIA participation. Subsequently, a logit model was used to estimate the effect of the independent herd factor variables (size, location and CDHIA participation) on the log odds of the dependent S. agalactiae variable. This model required conditioning on the three-way relationship among the independent variables.medium-sized, non-CDHIA herds in district 2 (northcentral California) showed the highest expected odds (3.37) for S. agalactiae in bulk tank milk, while small, CDHIA herds in district 3 (northcentral coastal California) produced the lowest odds (0.39).     

SCINTIGRAPHIC CHARACTERIZATION OF THE EQUINE FOREDIGIT AND METACARPOPHALANGEAL REGION FROM BIRTH TO SIX MONTHS OF AGE

Both foredigits and metacarpophalangeal joints of six Quarter Horse foals were scanned serially to six months of age using ⁹⁹Tc-methylene diphosphonate. Dorsal scans were made on day 1 and at two, four, six, ten, 14, 18, 22 and 26 weeks of age. Scans were assessed visually for distal third metacarpal, proximal phalangeal, and middle phalangeal physeal appearance and closure. Scans were also evaluated by computer region-of-interest (ROI) and line-profile analysis to characterize the physes quantitatively. Physeal region radioactivity relative to a disphyseal reference region was greatest at four weeks for all physes. Scintigraphic physeal closure of all physes occurred at approximately six months of age with a range of four and one half to greater than six months. The study was conducted to allow better assessment of diffuse and focal physeal disease by determining developmental times at which normal physeal region radioactivity has decreased enough to not obscure abnormal radioactivity and by quantifying scintigraphic physeal appearance which enables computer analysis to detect visually indeterminate physeal abnormalities.     

Two anatomic resources of canine pelvic limb muscles based on CT and MRI

Advances in magnetic resonance (MR) imaging and three-dimensional (3D) modeling software provide the tools necessary to create sophisticated, interactive anatomic resources that can assist in the interpretation of MR images of extremities, and learning the structure and function of limb musculature. Modeling provides advantages over dissection or consultation of print atlases because of the associated speed, flexibility, 3D nature, and elimination of superimposed arrows and labels. Our goals were to create a diagnostic atlas of pelvic limb muscles that will facilitate interpretation of MR images of patients with muscle injury and to create a 3D model of the canine pelvic limb musculature to facilitate anatomic learning. To create these resources, we used structural segmentation of MR images, a process that groups image pixels into anatomically meaningful regions. The Diagnostic Atlas is an interactive, multiplanar, web-based MR atlas of the canine pelvic limb musculature that was created by manually segmenting clinically analogous MR sequences. Higher resolution volumetric MR and computed tomography (CT) data were segmented into separately labeled volumes of data and then transformed into a multilayered 3D computer model. The 3D Model serves as a resource for students of gross anatomy, encouraging integrative learning with its highly interactive and selective display capabilities. For clinicians, the 3D Model also serves to bridge the gap between topographic and tomographic anatomy, displaying both formats alongside, or even superimposed over each other. Both projects are hosted on an open-access website, http://3dvetanatomy.ncsu.edu/     

Calibration of sulfate levels in the archean ocean

The size of the marine sulfate reservoir has grown through Earth's history, reflecting the accumulation of oxygen into the atmosphere. Sulfur isotope fractionation experiments on marine and freshwater sulfate reducers, together with the isotope record, imply that oceanic Archean sulfate concentrations were <200 microM, which is less than one-hundredth of present marine sulfate levels and one-fifth of what was previously thought. Such low sulfate concentrations were maintained by volcanic outgassing of SO2 gas, and severely suppressed sulfate reduction rates allowed for a carbon cycle dominated by methanogenesis.     

Intensive temporal and spatial sampling of polychaete biodiversity reveals significant implications for impact assessment and marine park design

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Effect of cultivated copepods (Acartia tonsa) in first‐feeding of Atlantic cod (Gadus morhua) and ballan wrasse (Labrus bergylta) larvae

The aim of this study was to compare the nutritional composition and effects of short periods with cultivated copepod nauplii versus rotifers in first‐feeding. Atlantic cod (Gadus morhua) and ballan wrasse (Labrus bergylta) larvae were given four different dietary regimes in the earliest start‐feeding period. One group was fed the copepod Acartia tonsa nauplii (Cop), a second fed enriched rotifers (RotMG), a third fed unenriched rotifers (RotChl) and a fourth copepods for the seven first days of feeding and enriched rotifers the rest of the period (Cop7). Cod larvae were fed Artemia sp. between 20 and 40 dph (days posthatching), and ballan wrasse between 36 and 40 dph, with weaning to a formulated diet thereafter. In addition to assessing growth and survival, response to handling stress was measured. This study showed that even short periods of feeding with cultivated copepod nauplii (7 days) had positive long‐term effects on the growth and viability of the fish larvae. At the end of both studies (60 days posthatching), fish larvae fed copepods showed higher survival, better growth and viability than larvae fed rotifers. This underlines the importance of early larval nutrition.     

A case-control study of Nocardia mastitis in Nova Scotia dairy herds

A case-control study was conducted to identify herd production, housing, and hygienic and therapeutic factors associated with a diagnosis of Nocardia mastitis in dairy herds in Nova Scotia. The data were collected by on-farm interviews with owners of 54 case and 54 control herds.

Logistic regression was used to study risk factors. The use of dry cow products containing neomycin, including two specific dry cow products, was strongly associated with a diagnosis of Nocardia mastitis in a herd. Other factors which increased the risk of Nocardia mastitis were higher levels of production, larger herd size, and a large percentage of cows treated with dry cow products. These results are compared to results from a similar study carried out in Ontario.